Case study of IMU loads and self-reported fatigue monitoring of water polo goalkeepers preparing for the Olympic games.

Introduction: Measurement of training in water polo goalkeepers has focused first on psycho-physiological variables, but also on external volume estimated with wearable sensors. However, there are limited studies exploring training monitoring in water polo goalkeepers longitudinally. Methods: Three female senior national team goalkeepers participated in this study from May to August 2021. Internal loads were defined using session rating of perceived exertion (sRPE). Tri-axial accelerations and angular velocities were measured with an inertial measurement unit (IMU) placed on the lower back to measure external loads. Relationships between self-reported and IMU-derived metrics were explored using Spearman correlations. Two-way ANOVAs were used to assess differences between session types and between athletes. Results: In total, 247 sessions were collected (159 practices, 67 matches and 21 game warm up), with 155 sessions having complete data. IMU metrics, such as number of kicks, number of jumps or player-load showed high correlation with each other (ρ = 0.80-0.88). There was also a moderate correlation (ρ = 0.47, 95% CI = 0.33-0.58) between sRPE and player-load measured with the IMU. ANOVA tests showed that there were significant differences between athletes for sRPE (p < 0.01) but not for player load (p = 0.47). There were no interactions between athletes and training types, except for index score (p < 0.01). Conclusions: This study shows that monitoring of training loads can be performed successfully in water polo goalkeepers using a combination of self-reported and IMU measures. Self-reported outcomes can be expected to vary significantly across athletes within the same session, while IMU metrics vary across training situations. Finally, coaches should be mindful of missing data, as they can skew the interpretation of training loads.

Monitoring Variables Influence on Random Forest Models to Forecast Injuries in Short-Track Speed Skating.

Injuries limit the athletes' ability to participate fully in their training and competitive process. They are detrimental to performance, affecting the athletes psychologically while limiting physiological adaptations and long-term development. This study aims to present a framework for developing random forest classifier models, forecasting injuries in the upcoming 1 to 7 days, to assist the performance support staff in reducing injuries and maximizing performance within the Canadian National Female Short-Track Speed Skating Program. Forty different variables monitored daily over two seasons (2018-2019 and 2019-2020) were used to develop two sets of forecasting models. One includes only training load variables (TL), and a second (ALL) combines a wide array of monitored variables (neuromuscular function, heart rate variability, training load, psychological wellbeing, past injury type, and location). The sensitivity (ALL: 0.35 ± 0.19, TL: 0.23 ± 0.03), specificity (ALL: 0.81 ± 0.05, TL: 0.74 ± 0.03) and Matthews Correlation Coefficients (MCC) (ALL: 0.13 ± 0.05, TL: -0.02 ± 0.02) were computed. Paired T-test on the MCC revealed statistically significant (p < 0.01) and large positive effects (Cohen d > 1) for the ALL forecasting models' MCC over every forecasting window (1 to 7 days). These models were highly determined by the athletes' training completion, lower limb and trunk/lumbar injury history, as well as sFatigue, a training load marker. The TL forecasting models' MCC suggests they do not bring any added value to forecast injuries. Combining a wide array of monitored variables and quantifying the injury etiology conceptual components significantly improve the injury forecasting performance of random forest models. The ALL forecasting models' performances are promising, especially on one time windows of one or two days, with sensitivities and specificities being respectively above 0.5 and 0.7. They could add value to the decision-making process for the support staff in order to assist the Canadian National Female Team Short-Track Speed Skating program in reducing the number of incomplete training days, which could potentially increase performance. On longer forecasting time windows, ALL forecasting models' sensitivity and MCC decrease gradually. Further work is needed to determine if such models could be useful for forecasting injuries over three days or longer.

Test-retest reliability of a hip strength assessment system in varsity soccer players.

OBJECTIVE: To investigate test-retest reliability of a hip strength assessment system (GroinBar). DESIGN: Test-retest reliability study. SETTING: Laboratory. PARTICIPANTS: Twenty asymptomatic varsity soccer players. MAIN OUTCOME MEASURES: Maximal isometric hip strength (adduction, abduction, internal and external rotation, flexion and extension) was assessed using the GroinBar. Intraclass correlation coefficient (ICC) and relative standard error of measurement (SEM) were calculated to evaluate reliability of peak (ICC3,1) (highest peak within 3 trials) and average peak (ICC3,3) (average of 3 trials) force and rate of force development (RFD). Hotelling's T2, were also used to compare bilateral and reciprocal ratios between dominant and non-dominant leg. RESULTS: ICC for both peak force and RFD values revealed moderate to good reliability (0.53-0.88 and 0.61-0.84, respectively), whereas reliability was good to excellent regarding their average values (0.77-0.95 and 0.81-0.92, respectively). SEM of average peak force and RFD values (4.1-9.4% and 8.2-13.9%, respectively) were lower than that of peak force and RFD values (5.7-13.0% and 10.7-19.1%, respectively). No significant difference was found in bilateral and reciprocal force ratios between dominant and non-dominant leg. CONCLUSIONS: The GroinBar is a reliable tool to assess hip muscle function in athletic populations and could be used for player screening and follow-up.

Cluster analysis using physical performance and self-report measures to identify shoulder injury in overhead female athletes.

OBJECTIVES: To evaluate the diagnostic validity of the Kerlan-Jobe orthopedic clinic shoulder and elbow score (KJOC) and the Closed kinetic upper extremity stability test (CKCUEST) to assess functional impairments associated with shoulder injury in overhead female athletic populations. DESIGN: Cross-sectional design. METHODS: Thirty-four synchronized swimming and team handball female athletes completed the KJOC and the CKCUEST during their respective team selection trials. Unsupervised learning using k-means algorithm was used on collected data to perform group clustering and classify athletes as Injured or Not Injured. Odds ratios, likelihood ratios, sensitivity and specificity were computed based on the self-reported presence of shoulder injury at the time of testing or during the previous year. RESULTS: Seven of the 34 athletes were injured or had suffered a time-loss injury in the previous year, representing a 20.5% prevalence rate. Clustering method using KJOC data resulted in a sensitivity of 86%, a specificity of 100% and a 229.67 diagnostic odds ratio. Clustering method using CKCUEST data resulted in a sensitivity of 86%, a specificity of 37% and a 3.53 diagnostic odds ratio. CONCLUSIONS: KJOC had good diagnostic validity to assess shoulder function and differentiate between injured and non-injured elite synchronized swimming and team handball female athletes. The CKCUEST seemed to be a poor screening test but may be an interesting test to evaluate functional upper extremity strength and plyometric capacity. Unsupervised learning methods allow to make decisions based on numerous variables which is an advantage when considering the usually substantial overlap in screening test scores between high- and low-risk athletes.

Evolution of muscular fatigue in periscapular and rotator cuff muscles during isokinetic shoulder rotations.

To this day, how shoulder muscles react to a strong fatigue stimulus during dynamic shoulder rotations remains unknown. The aims of this study were to assess the effect of repeated maximal internal-external isokinetic shoulder rotations on shoulder strength and muscle activity. Twenty-four individuals completed a 50-repetition fatiguing isokinetic protocol while electromyography was recorded on eleven muscles of the shoulder girdle. Time-frequency transformation and an ANOVA model using statistical parametric mapping methods were used to analyze shifts in instantaneous median frequency (MDF) between each 10-repetition Blocks. Peak torques decreased in both internal and external rotation (P < 0.01) by 24.8% on average which indicated the presence of fatigue. Significant decrease in MDF (P < 0.01) was observed for pectoralis, middle deltoid, upper, middle and lower trapezius, infraspinatus and subscapularis muscles. The observed fatigue to the periscapular and rotator cuff muscles suggests that shoulder stability could be compromised during repeated shoulder rotations, which could underlie the increased risk of scapular dyskinesis and shoulder impingement during fatiguing tasks. The present study provides a deeper understanding on the manifestations of fatigue within muscles of the shoulder girdle and the results could be applied toward improvements in athlete shoulder injury prevention and rehabilitation programs.

Muscle recruitment patterns of the subscapularis, serratus anterior and other shoulder girdle muscles during isokinetic internal and external rotations.

The aims of this study were to investigate the differences in peak muscle activity and recruitment patterns during high- and low-velocity, concentric and eccentric, internal and external isokinetic shoulder rotations. Electromyographic activity of the rotator cuff and eight superficial muscles of the shoulder girdle was recorded on 25 healthy adults during isokinetic internal and external shoulder rotation at 60°/s and 240°/s. Peak muscle activity, electromyographic envelopes and peak isokinetic moments were analyzed using three-factor ANOVA and statistical parametric mapping. The subscapularis and serratus anterior showed moderate to high peak activity levels during each conditions, while the middle and posterior deltoids, upper, middle and lower trapezius, infraspinatus and supraspinatus showed higher peak activity levels during external rotations (+36.5% of maximum voluntary activation (MVA)). The pectoralis major and latissimus dorsi were more active during internal rotations (+40% of MVA). Only middle trapezius and pectoralis major electromyographic activity decreased with increasing velocity. Peak muscle activity was similar or lower during eccentric contractions, although the peak isokinetic moment increased by 35% on average. The subscapularis and serratus anterior appear to be important stabilizers of the glenohumeral joint and scapula. Isokinetic eccentric training at high velocities may allow for faster recruitment of the shoulder girdle muscles, which could improve joint stability during shoulder internal and external rotations.